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Due to their outstanding mechanical properties, fiber-reinforced polymer composite (FRPC) structures have become a prominent research topic. Yet, to surpass existing performance limits, their design potential should be expanded beyond conventional empirical methods. Moreover, because of the high manufacturing costs, the protection of FRPC structures should be considered in the design phase to extend their service life. In this paper, we introduce an innovative configuration wherein metal coatings are strategically applied to the surfaces of FRPC structures. This technique aims to protect the internal matrix and fiber materials, and to inhibit the interlaminar delamination of composite laminates. Then, a corresponding full-scale topology optimization framework is built based on a density-based method. The coating, matrix, and fiber materials are considered collectively, avoiding issues such as excessive computation, non-convex optimization, and fiber discontinuity. Furthermore, a dual variable scale filtering (DVSF) method and its simplified scheme are presented to optimize coating thickness based on the physical information obtained from finite element analysis. Meanwhile, the co-evolution of solid topology and fiber morphology, driven by algorithms, facilitates the parallel optimization of multiple geometric features. Several typical examples, including wing ribs, are provided to illustrate the effectiveness and superiority of our approach, highlighting its engineering relevance. [ABSTRACT FROM AUTHOR]

In this paper, the wave propagation mechanics theoretical model of Y-shaped core sandwich metabeams with local resonators is established based on the spectral element method, and the flexural wave bandgaps and vibration isolation characteristics are studied. The reliability of the theoretical model of Y-shaped core sandwich metabeams is verified by the finite element method and experiment. On this basis, a deep learning-based intelligent design method for predicting the vibration transmission characteristics and structure design of Y-shaped core sandwich metabeams is proposed. A dataset is created using the theoretical model of wave dynamics, and deep neural networks are constructed to forward prediction of transmission characteristics and intelligent design of Y-shaped core sandwich metabeams, respectively. Results indicate that the bandgap range of Y-shaped core sandwich metabeams is 2.5 times that of Y-shaped core sandwich beams, and the start frequency of bandgap is reduced by 578 Hz. The prediction of the transmission characteristic curve is in good agreement with the target, and the average relative error of intelligent design is below 3 %, which verifies the precision of the intelligent design method. The innovative, intelligent design method provides a novel way to realize engineering vibration reduction design of acoustic metamaterials rapidly. [ABSTRACT FROM AUTHOR]

The combined effect of cyclic loading and steel rebar corrosion can determine the premature deterioration of reinforced concrete (RC) structures subjected to dynamic and environmental actions. The use of fabric-reinforced cementitious matrix composites (FRCM) is a promising solution to extend the fatigue life of RC structures. Externally bonded FRCMs are applied to the tension side of structural members to reduce the rebar stress level, thus delaying fatigue crack nucleation and/or propagation. A key aspect for the design of FRCM strengthening of these structures is the matrix-fiber bond behavior under fatigue loading. In this paper, a critical review of currently available studies on the fatigue behavior of FRCM-strengthened RC beams is presented. Then, the results of 25 bond tests on PBO FRCM-concrete specimens are provided and discussed. These tests include both single-lap direct shear and modified beam tests performed in quasi-static and cyclic mode. The results obtained show that the cyclic load may induce progressive debonding at the matrix-fiber interface with rupture of fiber filaments. Modified beam tests are more affected by these phenomena than direct shear tests. The rupture of fiber filaments is confirmed by the results of post-fatigue tests that show capacities lower than those of corresponding quasi-static tests. [ABSTRACT FROM AUTHOR]

The adhesively bonded structure, comprising carbon fiber-reinforced polymer (CFRP) and ultra-high-performance concrete (UHPC), enhances structural strength while reducing brittleness and strain softening behavior. However, the adhesively bonded structure is inevitably influenced by temperature variations throughout its service life. When the adhesive layer's temperature surpasses the glass transition temperature (T g), significant damage occurs to the bond layer joint. To investigate the debonding behavior of the CFRP-UHPC interface at various temperatures, a series of three-point-bending tests were conducted at room temperature, 120 % T g , 150 % T g , and 160 % T g. This study introduced a temperature degradation factor, employing a proposed maximum load capacity prediction formula to adjust both the test results and data from other researchers. By adjusting the cohesion parameters with the temperature degradation factor, a temperature-dependent mixed-mode cohesive zone model (CZM) was developed. The model's validity was confirmed through finite element (FE) analysis, considering two distinct experimental scenarios. The paper concludes that the proposed model effectively simulates interface debonding behavior across varying temperatures. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic stability of laminated cylindrical shell submerged in a fluid. Assuming that the fluid is incompressible satisfying the Laplace equation, the coupling relationship between the external pressure from fluid acting on the cylindrical shell and the velocity potential function of the fluid is deduced by using Bernoulli law. Based on Kárman-Donnell's thin shell theory, the governing equations for dynamic buckling of the composite laminated cylinder are established by introducing the constitutive relationship for laminated composite structures. Likely functions of the displacement and the stress function for cylindrical shell are proposed to construct Mathieu-Hill equation for dynamic stability of laminated cylindrical shell with fluid–structure interaction and the first three order dynamic instability regions are derived. A good agreement between the solutions from the proposed analysis and from the available literatures justified the accuracy and validity of the proposed analysis. With the established analysis, the influence of various parameters on the dynamic stability of cylinders are analyzed, from which a dynamic stability enhancement scheme suitable for composite laminated cylinders is summarized. It is found that the fluid–structure interaction will greatly reduce the excitation frequency of laminated cylindrical shells but has no effect on their vibration modes. [ABSTRACT FROM AUTHOR]

This paper investigated the quasi-static and dynamic behavior of 3D auxetic metamaterial structures made from carbon fiber reinforced polymer (CFRP) laminated composite. The aim of the study was to enhance design methodologies for load-bearing and energy absorption applications of these 3D novel structures, filling the research gap in understanding their response to quasi-static and especially dynamic loadings. The two novel 3D structures were designed and fabricated by using an interlocking assembly method based on the 2D auxetic CFRP sheets, which were formed with hybrid double-arrow-head with re-entrant and star unit-cells and made with plain weave carbon epoxy prepregs. The finite element (FE) method was adopted to analyze the mechanical characteristics of the structures under the quasi-static and dynamic loading, and Hashin failure criteria were used to define damage in the structures. The study showed that the designed 3D auxetic CFRP structures simultaneously exhibit superior auxeticity, load-bearing, and energy absorption capacity. [ABSTRACT FROM AUTHOR]

The composite shell is one of the crucial components of solid rocket motors. Its design goal is to reduce the shell mass as much as possible while ensuring technical and cost requirements. This paper proposes a damage analysis method for the thin-walled composite shell secondary loading process based on a refined finite element model to verify the damage caused by the thin-walled composite shell secondary loading process and the performance decline of the shell and to assist in the lightweight design of the thin-walled composite shell. The shell's damage failure state and crack propagation path are analyzed by establishing the acceptable finite element model and introducing the damage failure criterion and the stiffness degradation model. Based on the model, the damage state of the shell during the secondary loading process is described, and it is determined that the re-loading has little effect on the blasting performance of the shell. For composite shells used in small quantities, the effects of damage due to initial loading can be of no concern during design. This method can provide a theoretical basis for thin-walled composite shell safety factor selection and damage state assessment to achieve the thin-walled composite shell lightweight design goal. [ABSTRACT FROM AUTHOR]

• Investigate modal properties of edge waves in composite laminates. • Explore the sensitivity of edge waves in detecting edge delamination. • Provide examples of edge waves detecting delamination through experiments. Detecting near-edge damage in composite structural elements using guided wave-based techniques can be challenging, primarily due to the complexity of wave analysis arising from material anisotropy. Furthermore, scattered waves containing damage information can be contaminated by waves reflected from the edges, which makes detecting near-edge damage difficult to implement. In the literature, studies showed that in elastic materials, the edge of a structure can serve as a waveguide, enabling the existence of typical edge modes with concentrated energy at the edge. However, studies regarding edge waves in composite structures have received limited attention. This paper aims to explore the potential of detecting edge delamination damage in composite laminates using edge waves. The modal properties of edge waves in [(0/90) 2 ] s composite laminates are investigated using the Semi-Analytical Finite Element (SAFE) method. Additionally, dispersion curves for quasi-isotropic composite laminates are calculated. Following this, numerical and experimental studies were conducted to investigate the sensitivity of edge waves in detecting edge delamination in the [(0/90) 2 ] s composite laminates. The outcomes of this study offer physical insights into the modal properties of edge waves and confirm their effectiveness in detecting damage near the edges. [ABSTRACT FROM AUTHOR]

• The composite has a good energy dissipation characteristic. • The von Mises stresses on the skull are not enough to induce injury. • The Back Face Signature obtained are in line with standards. The research involved analyzing a material solution for a 9 mm Full Metal Jacket (FMJ) Parabellum loaded with ballistic impact on a resin laminate strengthened with extra aramid layers. The goal of this research is to determine the impact of material (aramid/DCPD) layer thickness on the energy absorption performance of the laminate for blunt trauma as blunt criterion (BC). For this purpose, aramid fiber laminate with dicyclopentadiene (DCPD) resin matrix was prepared. Laminate samples were tested on the drop test and were subjected to ballistic loads. The ABAQUS/Explicit program and finite element method were used to conduct the study. Individual material systems' optimal solutions were created using numerical analysis, and they were then classified using the mass-efficiency criterion. The numerical results were compared with the experimental using samples prepared according to the modeling methods. Selected results were shown and discussed in the later part of the paper. [ABSTRACT FROM AUTHOR]

This article presents a research study involving different simulations of crash tests by means of the finite element explicit dynamic software Ansys LS-Dyna to determine the roadworthiness of a fully composite chassis lightweight solar vehicle and its conformity to the World Solar Challenge (WSC) regulations. Furthermore, the paper describes the results of crash test simulations in conditions comparable with those of the standard homologation test, with an initial velocity of 15.5 m/s against a rigid barrier considering overlaps of 50% and 100%. The velocity measured at the base of the seat was later used in a sled test with a dummy to calculate the Head Injury Criterion (HIC), a number proportional to the probability of head injury caused by the impact. The values remained within the threshold of acceptability with overlap at 50% but exceeded the limit with the 100% overlap. With no load limiter implemented in the model, the seatbelt caused contact forces with the chest up to 14 kN against 6 kN of the typical load limiter used in road cars to limit damage to ribs and internal organs. Finally, the possibility of improving the front crash box was investigated by changing the crash box's planar sandwich structure with corrugated ones and layup without foam between the carbon layers. Various values of semi-amplitudes (A) of the sinusoidal profile have been tested. With a value of A of 6 mm, the capacity to absorb energy from an impact at 9 m/s was close to the original configuration. [ABSTRACT FROM AUTHOR]

Auxetic mechanical metamaterials contract or expand laterally when subjected to compressive or tensile load in the axial direction and offer potential benefits in areas such as flexible electronics, aerospace, and soft actuators. Nevertheless, when metamaterials are fabricated using conventional methods, their configurations and properties are fixed, which prohibits adaptation to the specific geometric requirements of their application environment. This limits their further development. This paper proposes an auxetic mechanical metamaterial with a negative Poisson's ratio and energy absorption capability. Compression specimens are fabricated with LCD photo-curable printing technology. The deformation mechanism and in-plane compression characteristics are examined through experimental and numerical simulation methods. The influence of unit cell geometrical control parameters on Poisson's ratio and energy absorption are also explored. The results indicate the dominant deformation mechanism of metamaterial during in-plane compression is bending deformation. The negative Poisson's ratio behavior is more pronounced when compressing along the X direction than along the Y direction, and the specimens also exhibit energy absorption capacity. In addition, the metamaterials prepared by 4D printing technology can be transformed from one configuration to another under external stimuli stimulation and force, and exhibit different mechanical properties, realizing programmable and reconfigurable, further expanding their application range. [ABSTRACT FROM AUTHOR]

Laminated composite structures, while offering weight savings compared with their metal counterparts, are susceptible to ply separation, (i.e., delamination mode of failure) due to the lack of through-thickness fiber reinforcements. In this paper, numerical simulations are used to gain an enhanced understanding of angled composite beam delamination when subjected to four-point bending consistent with the ASTM D-6415 test standard, with an expectation that the learning gained from this work is extensible to laminated composite components in general. While illustrating mesh sensitivity, manufacturing and frictional effects, four items of interest are examined: (1) the undamaged state/pre-peak load response, (2) the through-thickness peak tensile capability, (3) the post-peak load drop, and (4) the subsequent post-peak damaged response. A Finite Element Analysis (FEA) model is developed that incorporates the Smeared Crack Approach (SCA) to capture progressive failure modes within the element formulations directly, effectively eliminating the need for a priori specification of discrete delamination zones. The ability to incorporate failure directly within the element structure is particularly notable where laminates may not realistically permit a high number of interface layers or where geometry may be complex. Leveraging experimental data of curved composite laminates subject to four-point bending, the proposed approach successfully predicts the correct behavior throughout the damage progression. Additionally, this study offers an insight into effects of manufacturing-induced imperfections and frictions between the specimen and fixture on the prediction of inter-laminar strength of a curved composite part. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to evaluate the dynamic behaviour of sandwich toroidal shells composed of a core with negative Poisson ratio (auxetic honeycomb material) and nanocomposite enriched coating layers under impulsive/periodic pressures considering the geometrical nonlinearity. The set of nonlinear equilibrium equations based on the first-order shear deformation theory are and the resultant nonlinear differential motion equations are approximately solved by the Galerkin method and 4th-order Runge–Kutta solution, respectively. The achieved responses show that the amplitude of outward deformations is intensively increased when the proposed sandwich shells are subjected to rectangular periodic and impulsive loadings which shows the destructive effects of this type dynamic loading. The performed parametric studies shows that these destructive effects can be controlled by changing the geometrical properties of the honeycomb cells and the volume fractions of the nanocomposites in the coating layers. It is notable that in the previous studies the nonlinear dynamic response of toroidal shells subjected to various periodic and impulsive pressures was not investigated. However, in the present work, the mentioned dynamic responses were achieved and investigated without spending time-consuming computational. In fact, the novelty of this work is to develop such a robust and efficient tool. [ABSTRACT FROM AUTHOR]

• The bird-strike experiments on various M40J CFRP laminated square plates were performed with a wide range of impact velocities. • Numerical predictions of the bird-strike tests by the Finite Element (FE) Models agreed well with the experimental results. • The numerical model was employed to obtain a ply stacking sequence optimal in anti-bird-strike stiffness by the global optimization method. In this paper the anti-bird-strike behavior of M40J 12 K/7901 carbon fiber reinforced plastic (CFRP) laminates was investigated numerically and experimentally. Gelatin artificial birds were used to perform the bird-strike tests on various M40J CFRP laminated square plates with a wide range of impact velocities. Ultrasonic C-scan was utilized to measure the damage of the tested plates. Finite Element (FE) Models were created to simulate the bird-strike tests and the numerical predictions agreed well with the experimental results. The threshold values of bird's impact velocity V 0 when fibers begin to break were studied for 4 types of plates under normal and oblique bird-strikes to evaluate the anti-bird-strike capability of the laminates. The fiber damage after a flock-strike of two small birds was then investigated and the results suggest that the investigation of one large bird strike is more convincing in qualifying the anti-bird-strike resistance than that of a flock-strike of two small birds. Finally, a ply stacking sequence optimization in anti-bird-strike stiffness was obtained by the global optimization method. [ABSTRACT FROM AUTHOR]

• Experimental longitudinal tensile stress–strain curves fluctuated obviously before final failure. • Micromechanical model considers the dispersions of fiber strength and spatial distributions. • Predicted stress–strain curves agree well with experiments in modulus, initial failure and final failure. • Simulations show the progressive failure process of fibers before the final failure of the unidirectional composite. Longitudinal tensile failure prediction has always been the focus of research on unidirectional (UD) Carbon Fiber Reinforced Polymer (CFRP). In this paper, the longitudinal tensile tests of unidirectional T800 grade carbon fiber reinforced epoxy resin composite were carried out first. The experimental stress–strain curves show that there are obvious progressive damages before the final failures of the specimens. However, this phenomenon is usually neglected in most of the existing investigations and tests to only obtain elastic modulus and ultimate strength. Thus, a Representative Volume Element (RVE) model based on micromechanics was established using finite element method, considering the randomness of fiber spatial distribution and fiber strength. The tensile strength of fiber monofilaments was assumed to follow a statistical two-parameter Weibull distribution. The failure process of UD composite under longitudinal tensile load was simulated by explicit finite element method. The stress–strain curves obtained by simulation are in good agreement with the experimental results. Finally, the influence of different boundary conditions on the calculation of the RVE was studied. It is found that the final failure strengths of the RVE with uniform displacement boundary conditions are similar to the case of periodic boundary conditions, while the former has higher computational efficiency. [ABSTRACT FROM AUTHOR]

For fibrous materials such as nonwoven fabrics, paper and paperboards, inter-fiber bonds play a critical role by holding fibers, thus providing internal cohesion. Being a physical phenomenon, inter-fiber bonds occur at every fiber crossing and can be also geometrically detected. In relation to the idea, a statistical geometrical model was developed to investigate the effects of fiber geometry, (i.e. length and cross-sectional properties), spatial distribution, (i.e. location and orientation), and specimen size on fiber network connectivity, which refers to inter-fiber bonds at fiber crossings. In order to generate the fiber network, a geometrical fiber deposition technique was coded in Mathematica technical computing software, which is based on the planar projections and intersections of fibers and provided as supplementary material to the present article. According to this technique, fiber geometries in discrete rectangular prismatic segments were generated by using uniform distributions of the geometrical and spatial parameters and projected onto the transverse plane. Then, projected geometries were trimmed within the transverse boundaries of the specified specimen shape, rectangular prism in this particular study. After this step, fiber crossings were determined through a search algorithm, which was also used as the basis for the fiber spatial regeneration. Thereafter, fibers were accumulated on top of each other by taking fiber crossings into account and eventually fiber networks based on selected properties were formed. By means of the proposed technique, a series of simulation experiments were conducted on paper fiber networks to investigate the correlation between the fiber network connectivity and fiber length, cross-sectional properties, orientation and specimen length, width and thickness. [ABSTRACT FROM AUTHOR]

Pultruded glass fibre reinforced polymer (GFRP) profiles have low weight, high strength and corrosion resistance, but their brittle failure raises concerns about their use in seismic regions. Moreover, although their static monotonic response is reasonably well understood, the cyclic and hysteretic behaviour of GFRP frame structures and their beam-to-column connections have not yet been comprehensively investigated. This paper presents experimental and numerical investigations on the cyclic behaviour of a novel tubular GFRP beam-to-column sleeve connection system, comprising internal metallic parts. Four series of the connection system were tested, with varying number and position of the beam connection bolts, namely with: (i) one bolt in the webs (W1); (ii) two bolts in the flanges (F2); (iii) four bolts in the flanges (F4); and (iv) two bolts in the flanges with larger edge distance (F2S). The results show that series W1 presents the worst overall cyclic behaviour. On the other hand, the addition of bolt rows (F4 vs. F2) did not improve the cyclic response of the connection system. Conversely, increasing the edge distance (F2S vs. F2) led to significant improvements of the hysteretic behaviour, namely in the capacity to dissipate energy. Using the Pivot hysteresis model in the numerical study, a design-oriented model comprising frame and link elements was developed to simulate the response of the best performing series (F2S). In spite of its simplicity, the numerical simulation provided good agreement with the experimental results. In a companion paper, the behaviour of full-scale frames comprising F2S connections under monotonic and cyclic quasi-static sway tests was experimentally assessed. Numerical models of these tests were also developed to simulate the cyclic behaviour of the frames, using the parameters of the Pivot hysteresis model calibrated herein. [ABSTRACT FROM AUTHOR]

Composite frames in aerospace applications often show a lack of dimensional fidelity, which creates the necessity of costly shimming efforts within final assembly lines. A numerical study on C-profile frames has been performed to examine the mechanisms inducing these distortions. The paper shows that distortions are directly related to the composite's material architecture, the part geometry and interestingly also to the state of the art zone-based frame design philosophy applied today. The paper shows that frame distortions arise from the 3D orthotropic nature of composite laminates, in-plane CTE inhomogeneity of laminate zones and coupling of different part areas. The main mechanisms inducing frame distortions are deduced from the numerical models. The paper also shows that trimming operations, which are necessary to bring frames from the manufactured to the engineered shape, significantly affect the frames' final distortion state, the internal residual stress level as well as corresponding assembly forces during assembly. [ABSTRACT FROM AUTHOR]

In this paper, the Dual Mesh Control Domain Method (DMCDM) is used to carry out the free vibration and buckling analysis of two-constituent Functionally Graded Beams (FGBs) with through-thickness material variation. The material composition (modulus and density) is varied continuously through the beam thickness according to a power-law. The Euler-Bernoulli beam model consisting of the displacements and bending moment as the primary nodal degrees of freedom (i.e., mixed model) and the Timoshenko beam model with the displacement degrees of freedom (i.e., displacement model) are formulated as eigenvalue problems using the DMCDM. The numerical examples presented consider typical beam boundary conditions and various power-law exponents and slenderness ratios. The accuracy of this method is demonstrated by comparing the numerical results with those available in the literature. [ABSTRACT FROM AUTHOR]

• Low Velocity Impact analysis of Basalt/Flax/Aluminium bio-hybrid composite-metal joints was done using drop weight impact testing machine. • Three different stacking configurations i.e. sandwich, symmetric and asymmetric, were selected to investigate the effect of stacking sequence on the impact performance. • Asymmetric configuration has highest stiffness for initial failure. • The highest force withstood was by Asymmetric configuration hence it experienced least indentation and damage. • Symmetric configuration had the least resistance to impact at all energies used. A lot of composite materials with better impact resistance and better strength and stiffness can be manufactured these days. Many researchers have been using different materials to form new composites to understand their impact performance. This paper discusses such an attempt to make new composites by utilizing the concept of hybridization and then proposes which among them has better strength and performance under low-velocity impact (LVI) loading. In this work, circular patches of composites made up of a combination of basalt and flax fibers were used while being bonded with aluminum plate Al 2024-T3 of 3 mm thickness. The three different configurations which include asymmetric, symmetric, and sandwich were prepared using vacuum assisted bagging process and their impact performances were investigated using the Drop Weight Impact test. The results obtained were analyzed and they concluded that the asymmetric configuration of basalt/flax composite has better impact resistance, and strength and is better to use in structural components of automobiles, and the defense industry as compared to the other two. [ABSTRACT FROM AUTHOR]

Aluminum matrix foam composites have garnered significant interest among researchers due to their exceptional strength and energy absorption capabilities. However, the compressive strength of the hollow spheres in these composites is relatively low compared to that of conventional structural materials. As a result, the primary focus in developing aluminum matrix foam composites is to enhance their strength. Although researchers have conducted several reviews on the preparation methods and typical properties of these composites, less attention has been given to the factors influencing their strength and the structural design methods employed to bolster it. Therefore, this paper provides a comprehensive review of the factors impacting the strength of aluminum matrix foam composites and the available structural design options for strength enhancement. The summarization of structural design methods presented herein is crucial for gaining a deeper understanding of strategies to strengthen aluminum matrix foam composites. [ABSTRACT FROM AUTHOR]

Concrete-filled FRP tubes are gaining popularity among structures in areas with harsh environmental conditions. Despite their unique properties, FRP materials have poor resistance to elevated temperatures. This paper presents experimental and numerical investigations on the post-heating performance of concrete-filled pultruded GFRP tubes under concentric compression. Specimens were tested with different tube thicknesses of 3, 5, and 7 mm. The infill concrete was prepared with different compressive strengths of 30 and 60 MPa. Also, samples were exposed to five temperatures of 25,100, 200, 300, and 400 °C. Afterward, an axial compression test was conducted after the cooling process. The results indicated that the thickness of the tube was the most effective parameter in the axial load-bearing capacity of CFGFTs, while differences in the concrete's compressive strength did not influence the results significantly. Furthermore, the results showed that as the exposure temperature increases, the axial load-bearing capacity of the specimens decreases consistently. In addition, the comparison between the peak load values obtained from experiments and previously proposed models (codes and literature) showed that predictions for externally bonded FRP systems underestimate the peak load-bearing capacity. Finally, it is concluded that the results obtained from finite element analysis were in good agreement with the experiments. [ABSTRACT FROM AUTHOR]

• Investigation of the bending fatigue behaviour of composite repair systems using finite element analysis. • Evaluation of the effect of crack width of the host pipe, repair thickness, repair material and the level of loading. • Quantification of the relative contribution of the investigated parameters to the critical stress and fatigue life. Internal replacement pipe (IRP) systems are becoming an effective rehabilitation technique for legacy oil and gas pipelines with defects and discontinuities. Under repetitive traffic loads, the IRP-repaired pipes are subjected to fatigue. However, existing knowledge on the fatigue behaviour and remaining service life of IRP systems with circumferential discontinuities under cyclic bending is limited. Therefore, this paper investigated numerically the bending fatigue behaviour of legacy pipelines with circumferential discontinuities rehabilitated with IRP made from various material systems. The influence of the discontinuity width of the host pipe, thickness and elastic modulus of IRP, and level of traffic loading on the fatigue behaviour is evaluated. The results show that the tensile stress concentration at the discontinuity edge controls the bending fatigue behaviour of fully bonded IRP. The critical stresses and the minimum fatigue lifetimes are considerably influenced by the thickness and elastic modulus of the IRP systems, and the level of traffic loading while the width of the circumferential discontinuity has an insignificant effect. Multiple regression analyses show that the level of the traffic load has the most significant effect on the critical stress generated in the IRP, while the largest contribution to the minimum fatigue life comes from the elastic modulus of the repair material. [ABSTRACT FROM AUTHOR]

• The new laminated MFC plate is modeled via ANCF used the geometrical constraints. • Two Type MFC patches are considered in the rotating flexible MFC plate model. • The better vibration suppression is obtained by using neural network learning. The macro fiber composite (MFC) is a novel piezoelectric intelligent material, which is widely used in the field of vibration control due to its flexibility and larger actuation forces than PZT. In this paper, a laminated plate model considering the anisotropy of MFC is developed and applied to the vibration control of a rotating plate. The laminated plate is defined as a layerwise model, which deformation is described by the Absolute Nodal Coordinate Formulation (ANCF). The MFC laminated plate element contains 48 degrees of freedom (DOFs) where the effect of MFC element can be internally incorporated without increasing the DOFs of system. Simultaneously, a neural network PD control is adopted to control the vibration of the rotating plate. Eventually, static, dynamic, and modal analyses are performed to investigate the effects of different parameters. Several vibration simulations are carried out to illustrate the ability of MFC patches on vibration control. The findings in this article would be applied to mechanical prediction and control for rotor blades of helicopters, solar panels, etc. [ABSTRACT FROM AUTHOR]

Shear resistance prediction of reinforced concrete (RC) beams strengthened with externally bonded reinforcements (EBR) is a challenging task due to the complex nature of shear resisting mechanisms and their intricate interaction. Existing design models often overlook these dependencies, leading to significant variations in prediction accuracy. In this paper, a design model is proposed by integrating the most relevant shear resisting mechanisms based on the evidence demonstrated by a large database of experimental results from RC beams shear strengthened with wet layup carbon fibre reinforced (CFRP) sheets applied according to the EBR technique. The developed approach integrates the simplified modified compression field theory (SMCFT) with a regression-based model. A global sensitivity analysis was conducted according to which closed form equations were derived to obtain the tensile stress factor in cracked concrete and the inclination angle of the critical diagonal crack. A reliability analysis is carried out, and resistance reduction factors are achieved for different levels of reliability index. The database, composed of 284 RC beams shear strengthened with EBR-CFRP technique, is utilized to validate the proposed model, and compare its performance against some well-established existing design models. The results show that the proposed model, with an adequate framework for its use on design practice, outperforms the other considered models. [ABSTRACT FROM AUTHOR]

This paper proposes a numerical model to predict the pattern and features of the fracture surface and to understand the mechanisms and cause of the failure. Various fiber orientations of 0°, 90°, 0°/90° and ± 45° were utilized in the production of unidirectional glass-fiber-reinforced epoxy composites via the vacuum bagging technique. The mechanical properties of the manufactured composites were evaluated by measuring parameters including tensile strength, compressive strength, flexural strength and interlaminar shear strength. High-resolution scanning electron microscopy was used to examine the mechanisms of fracture in laminates. The mechanical properties of the composite material were found to be considerably improved when a unidirectional 0° fiber orientation was used, as compared to other fiber orientations. This was true for tensile, compressive, flexural and interlaminar shear loading modes. The composite laminates demonstrated several modes of breaking, including fibers pulling away from the matrix, holes in the matrix and river flow lines, depending on the direction of the fibers. The outcomes of the numerical simulation demonstrate a high level of fidelity with experimental findings. This study provides a valuable reference for predicting numerical analysis of the microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

• Thorough analysis of planar frame's free vibration using composite beams. • Comprehensive beam model with shear, warping, and in-plane/out-of-plane deformations. • Formulated continuity equations for frame's displacements and rotations. • FEM employed for accurate numerical solutions. • Results match ANSYS for torsional modes, surpassing prior research. This paper addresses the free vibration analysis of a general planar frame structure, consisting of an assembly of laminated composite beam members. A mathematical model is established for the beams by introducing a novel displacement field, which encompasses the influence of shear deformation, rotary inertia, material coupling, warping phenomenon, as well as in-plane and out-of-plane deformations. By incorporating these various factors, a comprehensive representation of the beam's behavior is achieved. The continuity equations for displacements and rotations of two adjacent members are formulated to derive the equations for the entire frame structure. The assembled equations are solved using the Finite Element Method (FEM). The numerical results obtained are compared with existing results in the literature and new results from 3D models in ANSYS. The present results for torsional modes are closer to the ANSYS results than the results of previous studies. An extensive analysis is performed to investigate the impact of various parameters, including stacking sequence, frame angle, relative frame length, and anisotropy ratios on the system response. [ABSTRACT FROM AUTHOR]

• Nonlinear vibrations of graphene-reinforced aluminum-based aero-engine blade are studied. • Three configurations for functionally graphene-reinforced gradient are considered. • New round of periodic-chaotic dynamic evolution is continued. • Aero-engine blade has rich and complex nonlinear dynamic behaviors. • Hyperchaotic, chaotic, almost periodic, period-doubling bifurcation are found. This paper analyzes the nonlinear dynamic behaviors of the graphene-reinforced aluminum-based aero-engine blade under the primary resonance using the amplitude-frequency response curves, bifurcation diagram, Lyapunov exponent and Poincaré map. The lateral aerodynamic load, longitudinal aerodynamic load, centrifugal force and temperature are investigated for the graphene-reinforced aluminum-based aero-engine blade. Three kinds of configurations for the functionally graphene-reinforced gradient are considered. The effective Young's modulus of the composite material is given by Halpin-Tsai mode. The rule of the mixture gives other material properties. The results demonstrate that the bifurcation diagrams of the modal amplitude for the blade with the lateral aerodynamic load, longitudinal aerodynamic load and temperature have the periodic-chaos dynamic evolution process under the disturbance of the engine rotation speed. When the disturbance amplitude reaches a specific value, a new round of the periodic-chaos dynamic evolution will be continued. The results also clearly indicate that the aero-engine blade has the rich and complex nonlinear dynamic behaviors which include the hyperchaos, chaos, almost periodic, typical period-doubling bifurcation and anti-period-doubling bifurcation vibrations. This research is more helpful for the engineers to understand the nonlinear dynamic behavior of the blade. [ABSTRACT FROM AUTHOR]

• Penetration mechanics of SiC/AA6061 FGM plates under ballistic impact is presented. • Failure behavior of the plates below and above the ballistic limit is scrutinized. • The compositional gradient is a significant armor design parameter. • The failure modes vary from ductile (metal-dense) to brittle (ceramic-dense). • Tailoring a continuous gradient provides tensile stress wave attenuation. This paper deals with a comprehensive experimental analysis of the penetration mechanics and failure mechanisms of SiC/AA6061 functionally graded plates under ballistic impact. The external, cross-sectional, and high-speed photographic damage and failure assessments of the plates were performed. The novelty of this study is to investigate the ballistic impact behavior of a ceramic/metal functionally graded plate with different compositional gradients in a wide range of impact velocities considering below and above the ballistic limit and to reveal a detailed analysis of the damage and failure mechanisms of the plate. This can provide fundamental insights into the design of ceramic/metal functionally graded armor materials. The results indicate that the metal-dense gradient plate shows localized ductile failures as ductile perforation and plugging, whereas the ceramic-dense gradient plate exhibits brittle failures as comminution and conoidal fracture. Tailoring a relatively continuous compositional gradient instead of an abrupt variation, namely the linear gradient, provides tensile stress wave attenuation and resistance to crack growth and fracture. [ABSTRACT FROM AUTHOR]

Curved surfaces may be approximated using polygonal panels to simplify complex architectural designs, yet their constructions can be expensive due to single-use moulds producing unique panels. To reduce costs, strategies like planarizing and reducing the number of different panels have been suggested, which are increasingly achievable with advancing digital fabrication technologies. However, current subtractive and additive manufacturing techniques face challenges in producing complex 3D shapes and large volumes, respectively. Combining these two techniques has been attempted, mainly with small 3D-printed nodes, leaving the direct realization of curved surface approximations unexplored. This paper extends the thick-panel origami theory to introduce planar-thick panels and 3D-printed gap fillers for cost-effective constructions. It presents a computational workflow to transform meshes into non-intersecting panels while preserving edge connectivity and frame-like gap fillers with minimized volumes. Physical prototypes demonstrate significant cost savings compared to direct 3D printing. All prototypes are accurate within a 10 mm material thickness due to the guidance of the gap fillers. The finite element analysis shows that structural performance is greatly influenced by the material properties, especially of panels, due to their relatively larger volume. Numerical examples are also presented using the k -means clustering-optimization method to reduce the number of different panels. • Curved surfaces are rationalized using planar panels and 3D-printed gap fillers. • A hybrid of subtractive and additive manufacturing processes is presented. • Planar-thick panels can be inexpensively cut without bevel requirements. • Frame-like gap fillers have minimized volumes to lower 3D printing costs. • One set of panels can be used to achieve various curved surface approximations. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D FE simulation of RC slabs strengthened with prestressed (0 %–50 %) CFRP-NSM system. • Fire resistance of prestressed CFRP-NSM system decreases with prestress level. • Fire resistance of prestressed CFRP-NSM system increases with fire protection. • Changes in distribution of CFRP stresses and bond stresses during fire exposure. • Numerical critical temperatures at CFRP anchorages ranged between 2.1 × T g and 3.6 × T g. This paper presents a numerical study about the fire behaviour of reinforced concrete (RC) slab strips strengthened with passive and prestressed carbon fibre reinforced polymer (CFRP) laminates installed according to the Near-Surface Mounted (NSM) technique. 3D finite element models were developed to simulate fire resistance tests in which the NSM-CFRP-strengthened-RC slab strips were simultaneously subjected to a service load and the ISO 834 fire. The CFRP-concrete interface was modelled through temperature-dependent bi-linear bond-slip laws. In addition to the prestress levels applied to the CFRP (0%, 25% and 50% of their tensile strength), the presence/geometry of fire protection (calcium silicate boards) was also assessed. The comparison between numerical and previous experimental results showed the models accuracy in predicting the thermo-mechanical response of fire exposed passive and prestressed NSM-CFRP-strengthened-RC slab strips, presenting a fire resistance decrease when the prestress increased from 0% to 50%, from 13 to 6 min when no fire protection was used, and from 152 to 127 min with fire protection. The numerical results allowed predicting the decrease of critical temperature in the CFRP anchorages with the prestress increase: 3.4–3.6 T g , 3.0 T g , and 2.1–2.4 T g respectively for prestress levels of 0%, 25% and 50% (T g – adhesive's glass transition temperature). [ABSTRACT FROM AUTHOR]

Mould free fibre reinforced composites are an emerging manufacturing process that allows for complex shapes to be produced, independently from complex moulding. Previous examples demonstrated reconfiguration through thermal stresses induced by an asymmetrical stacking sequence within a laminate. However, asymmetry within the laminate can adversely influence the stiffness and geometric coupling which results in heavier structures. This paper presents eccentric prestressing as a novel method to produce more structurally efficient mould free laminated composites. Euler-Bernoulli beam theory and finite element methods were employed to predict the strain and deformation of laminated composites with selective fibre prestress. The internal and external strains were measured with chirped fibre bragg grating sensors, and surface mounted strain gauges respectively to validate the numerical and analytical predictions where a difference of 3.13% was reported. Finally, a comparative study was conducted to show the benefits of eccentric prestress over asymmetric 4D printed laminates. [ABSTRACT FROM AUTHOR]

In this paper, full-field damage forecasting of a laminated composite structure under different low velocity impact (LVI) conditions is realized through the proposed surrogate model, named VQ-SM. First, an efficient surrogate modelling method is proposed based on the advanced Vector Quantised-Variational AutoEncoder (VQ-VAE) proposed by DeepMind. Second, numerical simulation based on the progressive damage model of composite laminates is performed to obtain the training dataset. After training, the performance of VQ-SM is evaluated compared to the surrogate model without a representation learning process. The results show that VQ-SM has better performance with high-precise and good robustness, trained on the small dataset. Finally, the impact damage field of composite laminates is analyzed based on the surrogate model. The proposed surrogate modelling method provides not only the full-field damage forecast model for composite structures, but also an efficient method of improving the performance of the "generative" surrogate model. [ABSTRACT FROM AUTHOR]

A novel design of the composite transformable/foldable rim of the spacecraft reflectarray antenna is presented in the paper. The rim is made in the form of anisogrid lattice toroidal shell split into six parts that are jointed using hinges containing helical springs. The springs create the moments required to deploy the antenna in orbit. A dielectric flexible flat membrane with reflective radiating elements generating a radio signal with required directivity is stretched on the rim. An algorithm of the finite-element model generation is developed for the toroidal rim using a typical finite-element unit cell of lattice structure. The lattice toroidal shell is modelled as a three-dimensional frame composed of curvilinear ribs. The results of design analysis of the lattice rim delivering a minimal mass to its structure subject to constraints imposed on the fundamental frequency, values of stress, and the buckling load factor are presented in this work. The corresponding set of design parameters of lattice structure, including the angle of orientation of helical ribs, number of helical ribs of one orientation, and size of the ribs' cross section are identified based on these results. [ABSTRACT FROM AUTHOR]

Vibration isolation is a promise to suppress mechanical vibration from a host structure, similarly, a mechanical vibration absorber, a simple but effective device to attenuate flexural wave propagation, which has been implemented in civil and mechanical engineering. This paper presents a type of composite sandwich phononic crystal to attenuate the flexural wave propagation in a beam structure, which can effectively suppress mechanical vibration in a broad band gap by repetitively arranging phononic crystal. First, the elastic wave dispersion characteristic in a composite sandwich beam structure is derived, and a triangular shape phononic crystal for flexural wave attenuation by taking advantage of destructive interference is presented. Then two dimensional phononic crystals are designed by assembling four different unit-cells of metabeam. Finally, numerical experiments are conducted to verify the effectiveness of the proposed mechanical metamaterial absorbers to attenuate flexural wave propagation, the numerical results indicate that the proposed metamaterial is of good performance in mechanical vibration suppression, which can effectively mitigate structure vibration in low-frequency domain than the structure without phononic crystal and single layer metamaterial beam structure. It is the first attempt to design a mechanical metamaterial absorber with the mechanism of destructive interference with composite sandwich phononic crystal. [ABSTRACT FROM AUTHOR]

• A new shear-strengthening philosophy was proposed to overcome the brittleness of FRP shear-strengthened concrete beams. • Both the ductility and shear strength were significantly enhanced by the proposed strengthening philosophy. • The new strengthening philosophy would not obviously increase cost and technical difficulties. • A new model was proposed to predict the V f of beams strengthened by the new shear strengthening philosophy. Due to the linear elastic stress–strain behavior of carbon fiber reinforced polymer (CFRP), the ductility of CFRP shear-strengthened reinforced concrete (RC) beams will be significantly reduced. Compared with shear capacity enhancement, increasing the ductility of CFRP shear-strengthened RC members is a much more challenging task, and a satisfactory solution has yet to be found. This paper introduces a new methodology that combines the brittle fiber reinforced polymer (FRP) with ductile rubber support composite (RSC) to form the FRP-RSC strengthening system. The variable stiffness RSC can adjust the stiffness of the strengthening system, which is achieved by the changed shear transfer actions in FRP, transverse reinforcement and concrete. Eight specimens were tested to evaluate the effectiveness of the FRP-RSC strengthening method. Experimental tests demonstrated that the displacement ductility with this FRP-RSC technique was 2.15 times that of the conventional externally bonded (EB) FRP strengthening, reaching remarkably 5.24. The mechanisms for enhancements in ductility, deformability and shear capacity were revealed. Poor matches were observed between the predicted FRP shear strength contribution (V f) per existing models and test data. A new model that can predict V f of FRP-RSC strengthened RC beams was developed, and better agreements between predictions and experimental results were obtained. [ABSTRACT FROM AUTHOR]

This paper extends sublaminate-based variable kinematics plate finite elements towards the buckling analysis of composite structures. Robust locking-free 4-node and 8-node interpolations are used to build the finite element matrices in terms of fundamental nuclei, invariant with respect to the employed kinematic model of the composite plate. Geometric nonlinearities are accounted for in the von Kármán sense. The classical linearized stability analysis is mainly conducted for sandwich panels, for which different kinematic assumptions are employed for the skins and the core. Global buckling of the sandwich panel as well as short-wavelength wrinkling of the skins are investigated by referring to a variety of case studies, including homogeneous and laminated skins as well as isotropic and orthotropic cores. Convergence studies are performed to establish the minimum number of elements for the local instabilities to be grasped. The proposed computational framework requires a simple 2D mesh and is capable of providing quasi-3D response patterns. This is as demonstrated by numerous case studies that address the transition from global to local buckling, the onset of wrinkling in flat sandwich panels with anisotropic skins under various loading conditions as well as the local face sheet instability occurring in sandwich panels working in bending. It is concluded that he proposed FEM-based tool is computationally efficient and can be advantageously employed in pre-sizing design phases without resorting to full 3D models. • Global buckling and wrinkling of sandwich structures is investigated. • Robust locking-free finite plate elements are implemented. • Reduced-order modelling strategies are assessed against 3D solutions. • Guidelines for determining effective computational models for wrinkling are proposed. • Skew wrinkling and one-sided wrinkling under bending are successfully computed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A nonlinear joint model with interface dynamic partitioning is proposed. • A dynamic model of the bolted VAT plate is established considering both joint and CFRC-material nonlinearity. • The frequency veering behavior of the bolted VAT plate caused by variations in boundary stiffness, connection stiffness, and fiber orientation is analyzed. • The nonlinear vibration responses of the bolted VAT plate are analyzed under the combined effects of modal interaction, joint nonlinearity, and material nonlinearity. To establish a dynamical modal of variable angle tow (VAT) plate accurately, the fiber path and fiber orientation of the VAT plate are described by high-order polynomials. Then, a simplified nonlinear joint model with interface dynamic partitioning is proposed to simulate the interface mechanical behavior of bolted joints. Based on these, a nonlinear semi-analytic dynamic model of the bolted VAT plate is built, which considers both material and joint nonlinearity and can accurately predict nonlinear vibration response. After verifying the proposed modeling method, a special bolted VAT plate is used as the analysis object for free vibration and forced vibration analysis. Firstly, the frequency veering behavior of the VAT plate caused by variations in boundary stiffness, connection stiffness, and fiber orientation is studied. Then, by analyzing the forced vibration response of the bolted VAT plate, it is found that under the combined effect of the modal interaction, material nonlinearity, and joint nonlinearity, the bolted VAT plate exhibited complex but rule-based nonlinear dynamic behavior. More importantly, the research work done in this paper has certain guiding significance for the optimization design of vibration resistance of a bolted VAT thin-walled structure with variable stiffness parameters and joint parameters as design variables. [ABSTRACT FROM AUTHOR]

• A novel meta -honeycomb was obtained and fabricated, which reversed the energy absorption method of traditional materials. • The enhanced bandgap property was established by multi-resonator. • The dynamic response of the meta -honeycombs was measured under the impact and blast loads. • The optimization of the meta -honeycomb was verified by coupling different resonators. Conventional honeycomb materials are difficult to resist multiple blast because the enormous energy generated by the explosion would cause plastic deformation of the material, which weakens the strength of the structure. In this paper, a novel meta -honeycomb is designed by adding local resonance system to hierarchical cells, which is based on the multi-resonator-enhanced bandgap property, to withstand multiple blast. This meta -honeycomb reverses the energy absorption mode of traditional honeycomb materials; that is, the energy absorption by plastic deformation of the material becomes the reflection of the stress wave through the equivalent negative mass property generated by the local resonance system, which significantly reduces the deformation of the material and the reaction force at the support under impact loads. In particular, for the secondary explosion loading, the maximum deformation of the meta -honeycomb is reduced by 74% compared with the traditional hierarchical honeycomb. Furthermore, it is demonstrated that the design of meta -honeycomb can be optimized by coupling the bandgap generated by the negative mass property, thereby improving the energy absorption efficiency. This research result provides a new concept for the design of blast-proof materials, which has a high potential for a wide range of engineering applications. [ABSTRACT FROM AUTHOR]

• The baking soda abrasive jetting method as a new surface material stripping method for glass fiber reinforced materials (GFRP) was studied. • The jetting effects of different abrasives were compared, and the advantage of low damage of baking soda abrasives was highlighted. • Chemical stripping method was used to compare cleanliness. • The surface material of GFRP stripping process was simulated using LS-DYNA. Glass fiber reinforced composites (GFRP) working in a specific environment require regular inspection and maintenance. It is necessary to remove the surface material of fiber reinforced composites to check the fracture of fibers and the damage to matrix that binds fibers in this process. In this paper, the baking soda abrasive jetting was utilized to strip the surface material of glass fiber reinforced epoxy resin (GFREP). The stripping effects of baking soda abrasive jetting technology under different jetting parameters (fiber orientation, jet angle, jet pressure) were explored, and the optimum stripping conditions were determined as parallel to the fiber, 30°, 0.4 MPa. Compared with the chemical stripping method (phenol-dichloromethane), baking soda abrasive jetting can better retain epoxy resin between glass fibers. The LS-DYNA was applied to simulate the erosion process of a single abrasive particle under the optimum stripping condition. The plastic deformation of the matrix and the slight bending deformation of the glass fiber under abrasive impact were observed. [ABSTRACT FROM AUTHOR]

• Elliptical concrete-filled FRP tubes with an embedded H-shaped steel (i.e., HS-ECFFTs) were tested under axial compression and cyclic lateral loading. • HS-ECFFTs performed with remarkable energy dissipation ability. Due to the effective FRP confinement, the local buckling of H-shaped steel was prohibited. • The elliptical aspect ratio had limited influences on the ductility, the stiffness degradation and the energy dissipation behavior. • The FRP thickness, after a certain threshold, showed beneficial but limited influences on the peak load, the stiffness degradation and the energy dissipation behavior. Concrete-filled FRP tubes (CFFTs) have found increasing applications due to their superior ductility and remarkable corrosion resistance. In published literature, circular CFFTs and rectangular CFFTs have been investigated extensively, while there are relatively few studies on elliptical CFFTs. There is no research about elliptical CFFTs with an embedded H-shaped steel (i.e., HS-ECFFTs) under axial compression and cyclic lateral loading. Against this background, this paper investigated the seismic behaviour of HS-ECFFTs experimentally and numerically. Test results indicated that: (1) all HS-ECFFTs performed well with remarkable energy dissipation ability; (2) due to the effective FRP confinement, the local buckling of the H-shaped steel was prohibited; (3) the elliptical aspect ratio had limited influences on the ductility, the stiffness degradation and the energy dissipation; (4) the FRP thickness, after a certain threshold, showed beneficial but limited influences on the peak load, the stiffness degradation and the energy dissipation; (5) the HS-ECFFT specimen performed much better in terms of the peak load, the ductility, the stiffness degradation and the energy dissipation when it was bending around the strong axis. The proposed numerical model established on the OpenSees platform could generate reasonably accurate numerical results for all HS-ECFFTs. [ABSTRACT FROM AUTHOR]

This paper presents a thorough experimental/numerical validation of optimised multi-material structures fabricated by material jetting technology. The proposed methodology uses, on the one hand, non-uniform rational basis spline (NURBS) entities to represent the geometric descriptor associated with each material phase constituting the continuum and, on the other hand, a general multi-phase material interpolation scheme to penalise the stiffness tensor of the structure. Two design requirements are included in the problem formulation: the lightness and the minimum length scale of each material phase. The influence of the integer parameters intervening in the definition of the NURBS entity and the influence of different combinations of material phases on the optimised solutions are investigated. The proposed approach is applied to 2D and 3D benchmark structures subjected to prescribed displacements representative of a three-point bending test. Based on the result of the topology optimisation process one of the optimised solutions, balancing the requirements of structural stiffness, lightness, and manufacturing constraints, is selected, manufactured and tested. A comparison between experimental and numerical results (obtained by non-linear analyses) is carried out to show the effectiveness of the approach. [ABSTRACT FROM AUTHOR]

• The piezoelectric bi-stable laminate configuration control was analyzed. • The influence of the driving voltage on the snap-through energy was discussed. • The preparation process of MFC piezoelectric bi-stable laminate was introduced. • Configuration theoretical results were verified by experiments. This paper studies the configuration change control and the snap-through phenomenon of bi-stable laminate with the MFC piezoelectric plate. The kinetic and potential energy expressions of the piezoelectric bi-stable laminate were obtained based on the von-Karman hypothesis. The constitutive equations of the system were given using a six-parameter displacement model, and the potential function of the system was derived using Hamilton's principle. The configuration changes of the piezoelectric bi-stable laminate under different geometrical conditions were analyzed. The influence of voltage on the bi-stable laminate configuration was studied by applying different driving voltages. The snap-through energy variation of the piezoelectric bi-stable laminate under different geometrical conditions was investigated. In the experimental part, the changes in bi-stable laminate configuration with different geometrical conditions and after attaching the piezoelectric plate were compared. Different driving voltages were applied to measure the difference in piezoelectric bi-stable laminate configuration, and the critical snap-through voltages were recorded. The measured changes in bi-stable laminate configuration and snap-through voltage at different voltages prove the correctness of the theoretical presentation. [ABSTRACT FROM AUTHOR]

The working environment of industrial fields where the Particulate Reinforced Composites (PRCs) are commonly used is complex. In these harsh environments, PRCs produce some nonlinear strains, such as plastic, thermal, and creep strains, which affect the performance of PRCs to some extent. In addition, the actual structure of PRCs contains a massive amount of inclusions, and the number of inclusions could reach the magnitude of millions or even tens of millions. For the large-scale numerical simulation of PRCs, ordinary displacement finite element requires a large number of meshes, which increases their computational complexity and unsolvability. For real PRCs with random particle distribution, homogenisation theory does not accurately capture the true state of stress concentration in PRCs. The Voronoi cell finite element method (VCFEM) can be a good solution to the drawbacks of the above two numerical simulation methods. The subject of the present work explores a modified complementary energy generalized function that takes the constitutive relationship of nonlinear strain into account, proposing a two-dimensional VCFEM, formulated with plastic, thermal, and creep strain. The simulation results are compared with the computed results of a commercial finite element software Marc to verify the validity and accuracy of the VCFEM. Results of the comparison show that the VCFEM has the advantages of simple meshing and faster computation under the same precision. The VCFEM, considering plastic, thermal, and creep strains proposed in this paper, lays the foundation for future large-scale numerical simulations of PRCs containing a large quantity of inclusion structures and can realistically capture the stress concentration state of PRCs. At the end of the article, the impact of the order of stress function on the calculation results is discussed. [ABSTRACT FROM AUTHOR]

• Investigating laminated glass failure under blast loading, optimizing accuracy and computational efficiency. • Hybrid techniques (FEM with erosion/deletion, SPH) yield optimal results for extreme loading. • Models replicate peak displacement, considering mesh distortion and energy dissipation. • Adaptive meshing crucial for accurate, homogeneous crack distribution in blast-loaded laminated glass. • Findings enhance understanding of laminated glass behavior, aiding protective structure design. Modeling laminated glass response to extreme loading scenarios is a computationally demanding process in designing and analyzing protective structures. Therefore, an optimal modeling scheme requires a delicate trade-off between accuracy and computational demand. This article investigates the failure modeling of laminated glass layups of thin and thick panels (three and 11 layers) under blast loading. This is done by implementing various simulation techniques: the finite element method with element erosion/deletion, the mesh-free method of smoothed particle hydrodynamics, and the hybrid implementation of mesh-based and mesh-free simulation through element conversions into particles. This Article examines the feasibility and limitations of each method, considering both the aspects of accuracy and computational cost in light of experimental testing results obtained from both arena and shock tube scenarios. Mesh sensitivity and the significance of adaptive meshing in capturing the fracture patterns are evaluated. The present paper suggests that using hybrid techniques leads to optimal modeling results. Furthermore, the stability of the modeling results under diverse blast conditions is verified. [ABSTRACT FROM AUTHOR]

Many research studies have been conducted to evaluate confinement-induced enhancements on the mechanical properties of FRP (fiber-reinforced polymers)-confined plain concrete elements subjected to axial compressive loading, leading to the development of extensive predictive models. Nevertheless, experimental stress–strain results for FRP-confined RC columns (FCRC) have demonstrated some behavioural features that cannot be simulated accurately through this kind of model, developed exclusively for FRP-confined concrete columns (FCC). In this paper, a new design-oriented stress–strain model is proposed for the prediction of load-carrying capacity versus axial strain relationship of FCRC. For this purpose, a new parabolic stress–strain expression is developed for calculating the first branch of FCRC's response up to the transition zone, followed by a linear function. New formulations are proposed to determine the first branch's stress–strain gradient, transition zone-related information and the second branch's slope, calibrated using a large test database of FCRC. The proposed design-oriented model is capable of simulating accurately the combined influence of the dual FRP and steel confinement on load-carrying capacity versus axial strain relationship of FCRC. Lastly, the capability of this model is validated by comparison to existing experimental data of FCRC and those obtained from some of existing models in the literature. [ABSTRACT FROM AUTHOR]

This paper presents the coupling between curvilinearity and effective modulus for a set of mathematically admissible high-symmetry and low-symmetry fiber architectures. The contour of the fiber is decomposed into a series of unidirectional short segments, and its effective modulus is determined using an integration scheme that combines theoretical analysis and finite element simulations. Results show that the modulus of low-symmetry sinusoidal and hyperbolic tangent fibers varies nonlinearly with orientation and controlled by the segments forming the smallest direction cosine with the loading direction. Both the orientation of the midline and amplitude of the fibers strongly influence the effective behavior. For unidirectional fiber reinforced composites, results reveal the existence of a critical fiber-orientation angle of 60 ° where the modulus is minimum. Fibers are the majority stress carrier below 60°, and above this angle, the matrix carries the load. The integration scheme can be applied to determine effective modulus of composites comprising fibers of arbitrary geometries and orientations, and the findings are expected to advance the design of additively manufactured complex composite structures. [ABSTRACT FROM AUTHOR]

Carbon fibre reinforced polymer (CFRP) structures benefit from electromagnetic riveting (EMR). However, incorrect riveting parameters could result in damages in CFRP structures during the EMR process. Excessive interference size may introduce initial damages to the joints. As a result, in this paper, the damage behaviours and the interference characteristics of the 30CrMnSiA/CFRP double-sided countersunk electromagnetic riveted joints are investigated. The riveting damage experiment was conducted, with the regular pressing riveting (RPR) process as a comparison. Moreover, a progressive damage FE model considering multiple typical damage modes of CFRP was developed for EMR damage prediction. The results show that when the rivet-hole diameter increases by 5 % (4.08 mm to 4.28 mm), the average interference size of the joint under EMR and RPR processes decreases by 41 % and 53 %, respectively. Double-sided countersunk riveted joint interference size along the rivet axial distribution is not uniform, the CFRP sheet side of the interference size is relatively small. The EMR achieves a tighter, more uniform interference fit, while causing more severe riveting damages to the CFRP structure. Initial riveting damage exhibits a variety of modes, with delamination damage showing most significant sensitivity to rivet hole clearance. [ABSTRACT FROM AUTHOR]

This paper proposes a reverse reconstruction method to generating accurately and high-effectively the meso-scale geometry modeling of 2.5D woven composites based on the deep learning. The method first segments the yarn from the X-ray computed tomography (Micro-CT) images based on the deep convolutional neural network (DCNN). Then, reconstruct the yarn surface model from segmented yarn images by using the marching cube algorithm. Consequently, the reverse model is generated by outlining the yarn surface model. Moreover, the yarn geometric parameters are analyzed to evaluate the geometric accuracy of the reverse model. Simultaneously, for the validation of the reverse model, the parametric model, the ideal model, and the experimental tests are considered. Where the parametric model and ideal model are established based on the geometric parameters of yarns. The results show that the DCNN is capable of accurately segmenting yarns from Micro-CT images with a global accuracy of 95.08%. The stiffness prediction error of the reverse model is only 0.706%, which is less than the error of the parametric model (3.77%) and much less than the ideal model. The reverse reconstruction method improves the efficiency of geomerty modeling by focusing on actural images rather than statistical parameters. [ABSTRACT FROM AUTHOR]

The dynamic responses of open-ended cylindrical shells with different polyurea layers under explosion load are studied in the current paper. The influences of polyurea thickness and position on the response characteristics of the composite shell are analyzed in detailed. The results indicate that the polyurea layer has significant influence the failure mode and energy absorption of the composite shell. Both polyurea in the interlayer and on the outer layer will decrease the bending moments of the composite shells of equal mass in the initial deformation process, which is easier to make the increase of the deformation heights of metal liner of composite shells with polyurea layers. The polyurea in the interlayer will weaken the constraint of metal liner, delay the fracture of fiber and restrain the bulking phenomenon of metal liner. With increase of polyurea thickness, the bulking phenomenon becomes less obvious and the deformation height of liner decreases non-monotonously. On the contrary, the outer layer polyurea will cause the bulking phenomenon of metal liner more obviously with increase of the polyurea thickness.But the outerlayer polyurea will restrict the deformation of the inner materials and limit the scattering of fiber fragment, improving the safety distance of the explosion vessel. In the whole process of anti-explosion, both polyurea in interlayer and outer layer absorb less than 10% of total energy, but they can significantly change the energy absorption of metal liner and fiber composite. [ABSTRACT FROM AUTHOR]